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Getting into the zone with OCT-angiography: A case study brought to you by the Centre for Eye Health

 

 

What type of disease is this?

a.      Principally retinal vascular

b.     Principally neurodegenerative

c.      Principally choroidal

d.     Principally systemic

 

Case

A 69-year-old man presented for routine annual review of his macula. His medical history was significant for benign prostatic hyperplasia and myocardial infarction, seven years prior to presentation. His regular medications include aspirin, bisoprolol, perindopril, atorvastatin, dutasteride and tamsulosin. He described longstanding visual distortions and vision loss in his right eye, affecting his reading fluency.

 

On examination, best-corrected central acuities were 6/15+2 OD and 6/7.5-2 OS. Central Amsler grid distortions were described in both eyes, worse in the right eye. Contrast sensitivity was similarly worse in the right eye at 1.48 log units OD and 1.56 log units OS using the Mars test. Anterior eye examination was normal. Dilated fundus examination and optical coherence tomography revealed hypo-reflective, inner retinal cavitation, draping of the internal limiting membrane, and outer retinal thinning at the temporal fovea in both eyes. There was also focal loss of the ellipsoid zone OD. OCT-angiography demonstrated juxtafoveal capillary telangiectasia, worse in the right eye. Fundus autofluorescence imaging also showed temporal depletion of macular pigment.

 

Diagnosis

Macular telangiectasia type 2

 

Answer

This type of disease is b. principally neurodegenerative.

 

Although macular telangiectasia type 2 was initially described as a primarily vascular condition, new insights into the pathogenesis has shifted the definition toward neurodegeneration with depletion of Müller cells forming a key component.1,2 The disease may be considered in two forms: a non-proliferative and proliferative stage. Interestingly, recent evidence using projection-resolved OCT angiography has shown that the development of retinal-choroidal anastomoses without subretinal neovascularisation may occur more commonly than previously observed, implying a further significant role of the choroid in the disease process.3 Although patients with MacTel 2 may feature a higher prevalence of diabetes mellitus, hypertension and other cardiovascular risk factors, sampling (ascertainment) bias cannot be completely excluded.4

 

 

Figure 1. Case images from the patient’s right eye. OCT-angiography findings are presented left to right in the following order: superficial vascular complex, deep vascular complex, and avascular layers.

 

 

Figure 2. Case images from the patient’s left eye. The order of images corresponds with Figure 1.

 

Macular telangiectasia type 2 is a rare entity first described by Gass in 1977. The peak incidence of symptoms occurs in the 5th and 6th decades.4 Clinical signs vary with the disease stage and degree of macular layer involvement.5 Characteristic features of the earlier, non-proliferative stage include vascular anomalies such as blunted dilated, right-angle venules, intraretinal crystalline deposits, loss of inner retinal integrity, fluid leakage, redistribution of macular pigment and pigment plaques, with associated and gradually progressive vision loss.4,6,7 In the later stages of the disease, retinal-choroidal anastomosis and proliferation of new vessels may occur leading to subretinal exudation and haemorrhage.3 Treatment of the proliferative stage using anti-vascular endothelial drugs has significant structural and functional benefits.8,9

 

Patient outcome

The patient’s file was reviewed closely under a telemedicine virtual care model by consulting ophthalmologists from the local health district to exclude neovascularisation. He was also educated about the importance of Amsler grid self-monitoring and in the absence of significant sudden visual changes or neovascularisation, ongoing annual surveillance will be required. With respects to his chief complaint, suggestive of binocular rivalry, he was advised to consider occluding one eye while reading and to return to the clinic for further advice or vision rehabilitation, as required.10,11

 

What is known on this topic

- MacTel 2 represents a relatively rare and principally neurodegenerative disease, with secondary vascular manifestations.1,2

- The non-proliferative subtype does not have an established treatment.8,12

- Key funduscopic features of MacTel 2 include bilateral, paracentral capillary telangiectasias and light grey zonal discolouration in the juxtafoveal superficial retina, often temporally. 

- Recent evidence using projection-resolved OCT-angiography implicates the choroid in disease pathogenesis.3

- Pigment alterations and morphological changes (including retina subsidence, designating the descent of the outer retina vessels toward the RPE) may confound the interpretation of OCT-angiography.3

 

What this case study illuminates

- Outer retinal atrophy, proliferation and remodelling (dilation) of the deep capillary plexus represent visually striking hallmarks of disease progression in the early, non-proliferative stage.

- Loss of the ellipsoid zone visualised using spectral domain optical coherence tomography is a key biomarker of disease progression and may be used as a simple classifier of disease severity.13

- Multimodal imaging, especially including OCT-angiography, has significant value in excluding macular neovascularisation.14,15

 

What evidence gaps remain

- There is a need for multicentre randomised controlled trials to establish treatment protocols for various stages of this condition.8

- Stronger evidence on the condition’s systemic associations (if any) are also required.4

 

Author

Dr Angelica Ly, BOptom (Hons), GradCertOcTher, PhD, FAAO

Lead clinician (Macula) and Integrated Care Co-ordinator, Centre for Eye Health

Associate Lecturer, UNSW Sydney

 

Dr Angelica Ly is a passionate clinician-scientist driven toward applying technology and systems-wide change for better, patient-centred care. She holds leadership positions at the Centre for Eye Health, on the Optometry NSW/ACT board of directors and on the editorial board of the journal Clinical and Experimental Optometry. Her current research interests include advanced retinal image analysis, patient outcomes, and health care delivery.

 

Acknowledgements

The author thanks Michael Yapp and Pauline Xu for reviewing the manuscript.

 

Disclosures

The Centre for Eye Health receives primary funding from Guide Dogs NSW/ACT.

 

References

1          Powner MB, Gillies MC, Zhu M et al. Loss of Muller's Cells and Photoreceptors in Macular Telangiectasia Type 2. Ophthalmology 2013; 120: 2344-2352.

2          Powner MB, Gillies MC, Tretiach M et al. Perifoveal Muller Cell Depletion in a Case of Macular Telangiectasia Type 2. Ophthalmology 2010; 117: 2407-2416.

3          Spaide RF, Yannuzzi LA, Maloca PM. Retinal-choroidal anastomosis in macular telangiectasia type 2. Retina 2018; 38: 1920-1929.

4          Charbel Issa P, Gillies MC, Chew EY et al. Macular telangiectasia type 2. Prog Retin Eye Res 2013; 34: 49-77.

5          Yannuzzi LA, Bardal AMC, Freund KB et al. Idiopathic Macular Telangiectasia. Arch Ophthalmol 2006; 124: 450-460.

6          Tzaridis S, Heeren T, Mai C et al. Right-angled vessels in macular telangiectasia type 2. Br J Ophthalmol 2019.

7          Sallo FB, Leung I, Zeimer M et al. Abnormal retinal reflectivity to short-wavelength light in type 2 idiopathic macular telangiectasia. Retina 2018; 38 Suppl 1: S79-s88.

8          Khodabande A, Roohipoor R, Zamani J et al. Management of Idiopathic Macular Telangiectasia Type 2. Ophthalmol Ther 2019; 8: 155-175.

9          Toygar O, Guess MG, Youssef DS et al. Long-term outcomes of intravitreal bevacizumab therapy for subretinal neovascularization secondary to idiopathic macular telangiectasia type 2. Retina 2016; 36: 2150-2157.

10        Tzaridis S, Herrmann P, Charbel Issa P et al. Binocular Inhibition of Reading in Macular Telangiectasia Type 2. Invest Ophthalmol Vis Sci 2019; 60: 3835-3841.

11        Finger RP, Charbel Issa P, Fimmers R et al. Reading Performance Is Reduced by Parafoveal Scotomas in Patients with Macular Telangiectasia Type 2. Invest Ophthalmol Vis Sci 2009; 50: 1366-1370.

12        Wu L, Evans T, Arevalo JF. Idiopathic macular telangiectasia type 2 (idiopathic juxtafoveolar retinal telangiectasis type 2A, Mac Tel 2). Surv Ophthalmol 2013; 58: 536-559.

13        Pauleikhoff D, Gunnemann F, Book M et al. Progression of vascular changes in macular telangiectasia type 2: comparison between SD-OCT and OCT angiography. Graefes Arch Clin Exp Ophthalmol 2019; 257: 1381-1392.

14        Villegas VM, Kovach JL. Optical Coherence Tomography Angiography of Macular Telangiectasia Type 2 with Associated Subretinal Neovascular Membrane. Case reports in ophthalmological medicine 2017; 2017: 8186134-8186134.

15        Tzaridis S, Hess K, Friedlander M et al. Optical coherence tomography-angiography for monitoring neovascularisations in macular telangiectasia type 2. Br J Ophthalmol 2020.